1. Field of the Invention
The present invention relates to a process for treating edible glyceride oils. More particularly, this invention relates to a process for treating edible glyceride oils to improve their storage properties, comprising treating edible glyceride oils with particular adsorbents and a bleaching earth in a determined sequence.
2. Description of the Prior Art
It is well-known that edible glyceride oils tend to develop "off-flavours" during storage, causing said oils to become less and less acceptable for edible purposes. To reduce the formation of off-flavours and to improve generally the storage properties of edible glyceride oil, it has therefore been common practice to subject the edible glyceridic oil to a refining treatment. However, even such edible oils may still show a tendency to form off-flavours, especially under prolonged storage conditions.
Various refining treatments are known in the art, the most common method being desliming, neutralisation, earth bleaching and steam deodorisation. However, particularly with glyceride oils which have already a strong unacceptable flavour of their own, such processes do not always yield an edible glyceride oil with satisfactory storage properties. It has now been found that by subjecting an edible glyceride oil first to a treatment with a suitable adsorbent, and subsequently to a treatment with a bleaching earth, significant improvements are achieved in the storage properties of the edible glyceride oil.
It has already been proposed in the art to treat edible glyceride oils with an adsorbent. Thus, British Patent Specification No. 865,807 describes a process for treating edible oils with activated alumina, in which process the oil is in solution in a non-polar solvent. The oil, preferably in unbleached condition, is passed through a column which contains the alumina, and subsequently deodorised with steam. Another proposal is given in French Patent Specification No. 990,704, according to which the oil, dissolved in a solvent, is passed through a column containing a silica gel. The oil may be a crude oil, or an oil which has undergone a bleaching treatment.